This invention relates to a machine for folding upwardly open cartons during reciprocation of a mandrel through a die assembly. The general nature of this type of machine is set out in U.S. Pat. No. 3,218,940 to Pearson, issued Nov. 23, 1965. The disclosure of this patent is herein incorporated by reference.
In the type of forming apparatus shown in U.S. Pat. No. 3,218,940 folding irons are located in opposition to one another for engagement at opposite sides of a carton blank forced between them. Each folding iron projects into the path of the carton bottom wall of each blank. Movement of the mandrel pivots the folding irons about their respective pivot axes. This apparatus is designed for conventional single thickness trays or carton blanks, having only a single set of end tabs which are folded about the upright corners of the tray or blank as it is formed and glued.
Many tray blanks, particularly those used for certain types of fresh produce, have double walls along one side and overlapping sets of tabs at each corner. However, such blanks cannot be moved through the die assembly shown in the prior Pearson U.S. Pat. No. 3,218,940, without the tabs being torn from the blanks by interference of the pivot shafts that support the folding irons.
The present invention was developed to remedy this problem and to provide a relatively simple mechanism by which tabs along one pair of side walls can be folded without this folding mechanism interfering with free passage of the remaining pair of side walls and extending tabs formed thereon. The details of this mechanism are shown in the drawings and described below.